This application claims priority to EP/01119262.2, filed Aug. 9, 2001 under the European Patent Convention and which is incorporated by reference herein in its entirety.
Arrangement of internally cooled electrical conductors, in particular for a generator rotor.
The invention relates to an arrangement of internally cooled electrical conductors, which in each case comprise a longitudinal conductor and a transverse conductor, in particular for a coil of a generator rotor. An internally cooled conductor is understood in particular as meaning a directly internally cooled conductor, by contrast with a radially cooled conductor.
Electrical conductors which are designed for high current intensities, such as the coils of a turbo-generator with a power of from about 450 MVA, are usually cooled by internal cooling ducts. In the cross section of a conductor or directly alongside the conductor cross section there runs at least one cooling duct, largely parallel to the conductor. A cooling fluid, in particular a cooling gas, preferably hydrogen, is passed with considerable velocity through the or each cooling duct, the fluid-mechanical design of the cooling duct having a direct effect on the flow velocity and the cooling effect and consequently on the achievable power of the generator. An electrical conductor of this type with a cooling duct is known for example from DE 195 43 392 C1. The flow resistance in the inlet region of the cooling duct is in this case reduced by spreading the conductor in this region.
In an internally cooled conductor, bending orxe2x80x94as a limiting case of bendingxe2x80x94buckling of the cooling duct contributes in particular to the flow resistance, the increase in the flow resistance attributable to the deflection of the coolant stream being all the greater the smaller the bending radius is. Inlet loss and outlet loss into and from the respective cooling duct must also be taken into account.
The electrical conductors of a generator rotor run substantially parallel to the axis of the latter, tangentially running conductor portions being connected to the axial conductor portions at the end faces in the region of what is known as the end winding. This connection between the conductor portions that are substantially perpendicular to one another can take place, as is known from DE-B 10 36 370, by bending of the conductor, the cooling duct following the bending all the way. Although this configuration of the conductor and cooling duct avoids buckling within the conductor and cooling duct, it is technically complex from production aspects on account of the bending of the conductor with the internal cooling duct.
In a comparatively simple way in terms of technical production, a tangentially or radially running conductor portion may be integrally bonded with an axially running conductor portion, in particular by soldering, the individual conductor portions in each case being straight and forming at least approximately a right angle. The soldering has the effect of closing the cooling duct or the cooling ducts of one of the connected conductor portions. For this reason, a separate gas inlet or gas outlet must be provided at the connecting point of conductor portions connected perpendicularly to one another. As a resultxe2x80x94in particular in the case of parallel arrangement of the cooling duct of the axial conductor portion on the one hand and the tangential conductor portion on the other handxe2x80x94a number of cooling ducts of lengths differing considerably from one another, in which the cooling fluid is heated to correspondingly different degrees, are formed. The different thermal loading of individual conductor portions has unfavorable effects on the achievable power of the generator.
The invention is therefore based on the object of specifying a favorable arrangement in terms of technical production of internally cooled electrical conductors, in particular for coils of a generator rotor, with suitable coolant conduction.
This object is achieved according to the invention by the features of claim 1. This provides that, in the case of a number of adjacently arranged conductors, which in each case comprise a longitudinal conductor and a transverse conductor connected to it, and the longitudinal conductors and transverse conductors of which respectively run at least approximately parallel to one another, a cooling duct of a longitudinal conductor of a first conductor is connected to a cooling duct of a transverse conductor of an adjacent second conductor.
The invention is based on the idea that the coolant conduction in an arrangement of internally cooled electrical conductors is to be considered independently of the current conduction. A direct connection of the cooling ducts of two conductor portions electrically connected to one another is not necessary. Conversely, the cooling ducts of conductor portions not electrically connected to one another may be connected fluid-mechanically. Since the achievement of a low flow resistance has priority in the design of cooling ducts, deflections should be avoided as far as possible. Furthermore, the individual cooling ducts should not vary too much in their length, to ensure adequately uniform cooling.
Within a conductor, a right-angled connection between a transverse conductor and a longitudinal conductor may be formed by the end face of the transverse or longitudinal conductor being connected to the wall of the other conductor portion by soldering. The cross sections of the two conductor portions may in this case differ from one another. Since, to avoid weakening the respective soldered connection, the cooling duct cannot be continued in a straight line through the soldered joint on the end face of the transverse or longitudinal conductor, the coolant has to be transported further at this location with a changed direction of flow, for example via a bore to be provided in the wall on the longitudinal side of this conductor portion or what is known as a recessed chamber. In the further transportation of the coolant, the number of deflections should be restricted to a minimum.
If, in the angle formed by one conductor, there lies an inner conductor formed in the same way from a transverse conductor and a longitudinal conductor, with the transverse and longitudinal conductors of the two conductors being arranged at least approximately parallel to one another a small distance apart, the end face of the transverse or longitudinal conductor of the inner conductor lies opposite a wall of the longitudinal or transverse conductor of the outer conductor. Consequently, a connecting duct can be provided between this free end face of the inner conductor and the cooling duct running in the opposite portion of the outer conductor. This connecting duct makes it possible in terms of fluid mechanics to conduct coolant from one portion of the inner conductor into a portion of the outer conductor arranged transversely thereto, or vice versa, with only one deflection.
The offset conductors differ in their length. In this respect, generally both the longitudinal conductor and the transverse conductor are longer in the case of an outer conductor than in the case of an inner conductor. The length of the angles lying in one another decreases from the outside to the inside. If the cooling ducts of the transverse and longitudinal conductorsxe2x80x94as part-conductors of a conductorxe2x80x94are respectively arranged in series, the outer conductor is therefore subjected to the greatest thermal loading. This loading is reduced by the connection of the cooling duct of the transverse or longitudinal conductor of the outer conductor to the cooling duct of the longitudinal or transverse conductor of the inner conductor. Taking this an analogous stage further, the part-conductor of the inner-lying conductor not connected to an outer part-conductor can, if appropriatexe2x80x94in the case of a total of a least three mutually offset conductors each with a transverse conductor and a longitudinal conductorxe2x80x94be connected to a part-conductor of a still further inward lying conductor. Consequently, two part-conductors of different conductors are respectively connected, with only a part-conductor of the outermost conductor and a part-conductor of the innermost conductor having separate cooling ducts. In this respect, the separate cooling of the outermost part-conductor is particularly favorable for limiting the thermal loading, on account of its great length in comparison with other part-conductors.
In the case of a number of cooling ducts running in or on a conductor, the use of only one cooling duct is often adequate. In this case, a connection between cooling ducts of different conductors is advantageously configured in such a way that a cooling duct in linear extension of the active cooling duct of one conductor leads only up to one of the cooling ducts of the other conductor which run perpendicularly to it, while the other cooling ducts, respectively, of the conductors are shut off, for example by closure plugs.
Arranged between individual conductors or conductor clusters, running substantially parallel to one another, for example of a coil, is a support, which both performs a mechanical function and keeps the individual conductors or conductor clusters at a distance, isolated from one another. The connecting duct leads through this support or a free space produced by the arrangement of supporting elements of this type. In addition, a further connecting duct may also be provided through the support, between one of a number of cooling ducts of a part-conductor and a cooling duct of a further part-conductor of the same conductor.
The advantages achieved thereby are, in particular, that on the one hand a number of cooling conductors are used in or on a conductor cross section. On the other hand, only a partial stream of the cooling fluid flowing in or on a part-conductor is conducted via a relatively long conducting channel bypassing the soldered connection with respect to a connected part-conductor to the latter, while another part of the cooling fluid flows via a comparatively short and straight connecting duct into a cooling duct of another conductor. Since it is designed only for a partial stream of the cooling fluid, the connecting duct bypassing the soldered connection may have such a small cross section that it is accommodated within the support and does not weaken it in practice. Since the cooling fluid flowing through this bypass duct undertakes part of the cooling work, the flow velocity of the cooling fluid can be reduced, resulting in a low power requirement for the circulation of the cooling fluid. Therefore, with the same flow velocity, the power can be increased, and consequently in the case of a generator the generator power can be increased.
For the outlet of the cooling fluid from a cooling duct, there may be provided, for example, in a way known per se, bores or recessed chambers which are led through a number of conductors and cooling ducts lying radially one above the other in a coil of a generator rotor. To achieve a specifically desired distribution of the various cooling fluid streams, it is possiblexe2x80x94as is known from DE 195 43 392 C1xe2x80x94to arrange a cooling duct insert in a cooling duct. It can be determined in this way which cooling fluid stream escapes from the conductor by which path.
The advantages achieved by the invention are, in particular, that uniform cooling is achieved with low pressure losses by the fluid-mechanical connection between cooling ducts of different conductors. As a result, the power required for circulating the cooling fluid is reduced and the possible current intensity in the conductors is increased, so that altogether a more favorable overall energy utilization of the generator is achieved.